Chisel Edge and Pilot Hole Effects_导向孔和横刃.pdf

Chisel Edge and Pilot Hole Effects in Drilling Composite Laminates Previous studies have shown the severe limitations that have to be placed on machining forces when drilling composite laminates due to their propensity for delamination. Delamination, which consists of separation between the plys in a laminate, is due to the M. S. Won relatively poor strength of these materials in the thickness direction. In drilling, delami- nation is initiated when the drilling force exceeds a threshold value, particularly at the C. K. H. Dharan critical entry and exit locations of the drill bit. While abrasive machining results in damage-free holes in most composites, such processes are slow and expensive when Department of Mechanical Engineering, compared to drilling with conventional twist drills. Here it is shown that the chisel edge University of California at Berkeley, in such drills is a major contributor to the thrust force that is the primary cause of Berkeley, CA 94720 delamination when drilling composite laminates. In this study, a series of drilling experi- ments were conducted on carbon fiber-reinforced composite laminates to determine quan- titatively the effect of the chisel edge on the thrust force. In addition, tests were conducted